DIAGNOSIS Yeah, this one's common. The 'CLEAN' light is a hard timer, not a sensor. It triggers after a set number of brewing cycles, regardless of your descaling efforts.
FIX You need to run the dedicated cleaning cycle to reset it. Fill the reservoir with a full carafe of fresh, cold water (no vinegar or cleaner). Add one tablespoon of white vinegar or a commercial coffee maker cleaner to the empty carafe. Place the carafe back on the warmer. Press and hold the 'CLEAN' button for 3 seconds until it beeps and the light starts blinking. Let the full cycle run—it'll pump the water/vinegar mix through and then flush with plain water. The light will go off when it's done.
IF THAT DIDN'T WORK If the light persists, the cycle might have been interrupted. Unplug the unit for a full 5 minutes to let the internal controller reset. Plug it back in and try the cleaning cycle procedure again from the start.
HEADS UP Don't ignore this light. If you bypass it by just unplugging and replugging to brew, mineral scale can eventually clog the internal thermoblock heater, which is a much more expensive fix.